It is known that X-ray diffractometers are very useful in analyzing certain materials. Generally, micro diffractometers are comprised of an emitter which generates an X-ray having a very small diameter, usually on the order of less than 50 .mu.m. From an operational standpoint, the X-ray is used to illuminate specific points on the material to be examined. The X-ray which impinges upon the sample is scattered with the scattered radiation measured by means of a detector.
During the measurement process, the emitter and/or the sample and/or the detector are rotated around the zero point of the diffractometer. The zero point is that point which is located at the surface of the sample material which provides proper distance between the X-ray source, the sample and the detector, and is in effect the precise portion of the sample that is being examined. Generally, this spot is mathematically defined as that area which satisfies the relation .theta.-/2-.theta. whereby .theta. is the angle of incidence between the X-ray and the sample.
Accordingly, in order to perform this analysis the X-ray must be very carefully positioned so as to be exactly on the surface point to be examined. Unfortunately, during analysis, X-ray radiation is both invisible to the human eye and hazardous to human health. Therefore, it is very difficult to properly align the sample sometimes requiring trial and error. Hence, as previously mentioned, the emitter and/or the sample and/or the detector are rotated during X-ray emission thereby insuring that proper alignment occurs at least occasionally during the evaluation. Accordingly, this has a tendency to require more time than is absolutely necessary, and will also generate more data, the bulk of which is irrelevant to the portion of the sample which is of interest.
Accordingly, it is an object of the present invention to produce an X-ray microdiffractometer which enables reliable and simple positioning of the focal spot of the X-ray on the sample. It is yet another object of the present invention to produce the aforementioned reliable and simple positioning while the focal spot lies in the zero point of the system.
It is yet another object of the present invention to produce a device which minimizes the amount of time required to irradiate the sample.
Still another object of the present invention is to produce a device which does not produce inordinate amounts of undesired or spurious data.
Finally another object of the present invention is to produce an X-ray microdiffractometer having a means for positioning a sample, a positionable X-ray emitter for generating a small diameter X-ray, a movable sample carrier for holding the sample and thereby moving the sample within three space coordinates, a detector positionable so as to be aimed at the zero point of the diffractometer while said X-ray emitter and the sample carrier are rotated around the zero point, a light source for generating a visible small diameter light beam, the light source aimable at the zero point, a camera having an optical axis, the camera aimable such that the optical axis passes through the zero point and forms an angle with the light beam of the light source so as to visibly indicate the zero point and the position of the sample with respect to the zero point.